| Displacement | 770t surface, 1080t submerged |
|---|---|
| Length | 74.2m oa |
| Width | 6.1m |
| Draught | 3.7m |
| Machinery | 2-shaft diesel/electric motor, 2600bhp surface, 1200shp submerged |
| Speed | surface 17kt, 9kt submerged |
| Range | 6000nm/10kt surface, 85nm/4kt submerged |
| Armament | 4-53cm TT, 1-8cm/28cal AA gun, 1-7.7mm MG |
| Complement | 45 |
| Name | Plan | Builder | Laid down | Launch | Complete | ||
|---|---|---|---|---|---|---|---|
| Ro-26 (SS-45) | FY1918 | Sasebo NYd | 1921. 3.10 | 1921.10.18 | 1923. 1.25 | SS2 (SS-45) | 1924.11. 1 renamed (Ro-26) 1940. 4. 1 disc |
| Ro-27 (SS-58) | FY1918 | Yokosuka NYd | 1921. 7.16 | 1922. 7.22 | 1924. 7.13 | SS2 (SS-58) | 1924.11. 1 renamed (Ro-27) 1940. 4. 1 disc |
| Ro-28 (SS-62) | FY1918 | Sasebo NYd | 1921.11.10 | 1922. 4.13 | 1923.11.30 | SS2 (SS-62) | 1924.11. 1 renamed (Ro-28) 1940. 4. 1 disc 1948. 5 BU |